Manufacture of hollow artificial textile fibers

ABSTRACT

267,187. Tennant, W. J., (Rousset, J.). Nov. 11, 1925. Cellulose acetate, cellulose nitrate, and other cellulose derivatives, processes for making filaments from. - Hollow artificial filaments are made by dry spinning a normal solution of a cellulose ester &amp;c. by extruding the solution into air or other gaseous medium at a temperature which is substantially higher than the boiling point of the solvent employed in the solution, the filaments at the moment of extrusion being subjected to an active superficial evaporation by maintaining a comparatively high rate of flow of the gaseous medium. With cellulose acetateacetone solutions, a suitable temperature range is 90-155‹ C., although the best results are obtained between 100-120‹ C.; in the case of nitrocellulose solutions in alcohol-ether, satisfactory results are obtained at 90-100‹ C. Specifications 189,973 and 248,696 are referred to.

Patented UNITED STATES PATENT OFFICE.

JOSEPH EDOUARD GIISTAVE LAHOUSSE, OF TERNAY, FRANCE, ASSIGNOR 'I.O SOGIE'IE i POUR LA FABRICATION DE LA SOIE RHODIASE'I'A, OF PARIS, FRANCE.

MANUFACTURE or HOLLOW ARTIFICIAL TEXTILE FIBERS.

No Drawing. Application filed October 25,

The manufacture of artificial fibers by-the so-called dry-spinning method, that is, by extruding into an evaporatingmedlum contained in a practically closed cell a solution of nitrocellulose, cellulose acetate or other cellulose derivative in a-volatile solvent or solvent mixture, is a well-known op' eration which is practiced industrially. The cross-sections of filaments obtained by the above method may be of various shapes, for example, rounded or flat, and hereinafter the general term full-shaped will be used to define these ordinary dry-spun filaments in contrast to hollow dry-spun filaments, the manufacture of which is the object of the present invention. A

It has now been found possible to obta n by the dry-spinning process hollow artificial filaments by employingthe ordinary solutions of cellulose acetate, nitro-cellulose or other cellulose derivative commonly used for .the manufacture of full-shaped filaments,

without adding to said solutions any special compound.

Hereinafter the ordinary solutions referred to above will be descrlbed simply as normal solutions. I

According to the present invention, hollow filaments are. manufactured by the dry-spinning process from a normal solution of a cellulose derivative by maintaining 1n the zone of birth of the filaments a temperature substantially higher than the boiling point of the volatile solvent and by producing simultaneously on the filaments an active superficial evaporation by means of a suitable regulation of the rate of flow oft-he hot gaseous medium "within the spinning cell.

In carrying out the present process no addition of a gas-evolving body is required.

It was not possible to foretell that the evaporating conditions described above would lead to the production on an industrial scale of really hollow fibers. It was naturally to be expected that, in view of the violence of solvent vapours, a continuous filament would not be produced or in any case that'the filament would not be continuouslyhollow along substantially its whole length. In fact, however, it has been proved that b following the process according to this invention a fiber is obtained whereof the 1926, Serial No. 144,173, and in Great Britain November 11,

constituent filaments are substantially hollovt 'throughout their length, and the fiber has a lustre comparable with that of ordiperature prevailing in the extrusion zone does not affect excessively the temperature, and therefore the viscosity, of the" solution,

which, prior to. extrusion, is present in the spinning devices.

The evaporating conditions under which the process is carried out Will vary with the volatile solvent employed, thetemperature inthe .zone ofbirth of the filaments being always substantially higher than the-boiling point of the solvent. solutions in acetone, a. suitable temperature in the zone of birth of the filaments is 100120 C. At temperatures between 90 For cellulose acetateand 100 0., the filaments contain a certain number of bubbles but the full benefits of a substantially hollow, filament are not secured. Satisfactory results have been obtained from cellulose acetate solutions in acetone at a spinning temperature of 155 (3., but as a general rule it will not be necessary or desirable to increase the temperature much above 120 W'ith nitrocellulose solutions in alcoholethegsatisfactory results have been obtained with temperatures ranging between and 100 C.

The evaporating conditions will also vary with the other conditions of spinning, for

example, the speed, the concentration of the solution and the size of the filaments, but it must be borne in mind that the two requirements hereinbefore specified, i. e., active evaporation creating immediately aliard envelope and high temperature producing the boiling of the remaining solvent, are simultaneously' necessary. v

Some examples according to the invention will be now described.

Example I.

lutionwas'extruded through a nozzle provided with thirteen holes each having a diameter of 0.10 mm. The speed was 75 metres per minute and the size of each fila ment was 10 deniers. The temperature in the zone of birth of the filament was 110 (3., and the rate of flow of the hot air circulating in the cell was 10,000 litres per hour.

The filaments were found to be tubular, to have a gloss similar to that of full-shaped artificial silk, and to have a density of 0.9.

Ewample H.

In this example the flow of the circulating hot air was reduced to 8,200 litres per hour, but otherwise the spinning conditions were the same as in Example I. The filaments produced were no longer hollow but fullshaped. This example shows clearly the necessary influence of an immediate active superficial evaporation.

Example [11.

spinning, 41 metres per minute. The fila-' ments produced according to this example were glossy, substantially hollow and had a density of 0.66.

What I claim and desire to secure by Letters Patent is '1. A dry-spinning process for the manu facture of hollow artificial fibers from a solution the base of which is a cellulose derivative, which consists in using a normal solution such as is commonly used for obtaining full-shaped filaments, spinning said solution into a hot gaseous medium at a temperature which is substantially higher than the boiling point of the solvent employed in the solution, and simultaneously submitting the filaments, as soon as extruded from the nozzles, to an active superficial evaporation by regulating the rate of flow, of the hot gaseous medium in the spinning cell.

2. A dry-spinning process for-the manufacture of hollow artificial fibers from a solution the base of which is a cellulose derivativc, which consists in using a normal solution such as is commonly used for obtaining full-shaped filaments, spinning said solution in hot air at a temperature which is substantially higher than the boiling point of the solvent employed in the solution, and simultaneously submitting the filaments, as soon as extruded from the nozzles, to an active superficial evaporation by regulating the rate of flow of the hot air in the spinning ce y In testimony whereof I have signe name to this specification.

JOSEPH EDOUARD GUSTAVE LAllOUSSE. 

